***Failed pre-smog sniffer***
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,298
Likes: 4
From: American Canyon Lethal Injection
***Failed pre-smog sniffer***
Sure did. Now what could have caused the high HC and CO readings.
I have mods of course. H/C and long tube headers with high flow cats.
Could this be because of bad O2 sensors or a bad tune.
I had codes set by the right bank O2 sensor and I cleared it and the CEL went out, this was a few weeks before going in for the pre-test.
15 MPH HC MAX 54 MEAS 129 ....CO MAX 0.50 MEAS 1.12
25 MPH HC MAX 37 MEAS 178.....CO MAX 0.47 MEAS 1.41
Thanks,
Sleeper
I have mods of course. H/C and long tube headers with high flow cats.
Could this be because of bad O2 sensors or a bad tune.
I had codes set by the right bank O2 sensor and I cleared it and the CEL went out, this was a few weeks before going in for the pre-test.
15 MPH HC MAX 54 MEAS 129 ....CO MAX 0.50 MEAS 1.12
25 MPH HC MAX 37 MEAS 178.....CO MAX 0.47 MEAS 1.41
Thanks,
Sleeper
Melting Slicks
Joined: May 2000
Posts: 2,498
Likes: 4
From: Brentwood TN
[QUOTE=SleeperC5;1561470487]I have mods of course. H/C and long tube headers with high flow cats.QUOTE]
Well let's see. A lumpy cam and flunk the sniff test. Hmmmmmm. I think a better tune is in order.
I think THE question on EVERY California Vette owner is how you got the long tubes past the check/expect to get the LT's past the check. The high flow cats are harder to light off and they are far enough from the cylinder to mean the exhaust temp is down as well. I don't know if it will help, or if this will keep enough residual heat to keeps the cats cooked off, but jump on the freeway and drive at maximum allowable speed for 30 minutes or so and then check the sniffer again. And IF this works, please DO tell us how you got the LT's past the inspection.
Charlie
Well let's see. A lumpy cam and flunk the sniff test. Hmmmmmm. I think a better tune is in order.
I think THE question on EVERY California Vette owner is how you got the long tubes past the check/expect to get the LT's past the check. The high flow cats are harder to light off and they are far enough from the cylinder to mean the exhaust temp is down as well. I don't know if it will help, or if this will keep enough residual heat to keeps the cats cooked off, but jump on the freeway and drive at maximum allowable speed for 30 minutes or so and then check the sniffer again. And IF this works, please DO tell us how you got the LT's past the inspection.
Charlie
Race Director
Joined: Aug 2006
Posts: 13,542
Likes: 1
From: Are you fat because you're lazy or lazy because you're fat? San Jose, CA
Cruise-In X Veteran
St. Jude Donor '09
What are the cam #'s again?
My guess might be bad cats? Aftermarket cats are notorious for not lasting as long as OEMs.
If that isn't it, then definitely look into tuning issues.
My guess might be bad cats? Aftermarket cats are notorious for not lasting as long as OEMs.
If that isn't it, then definitely look into tuning issues.
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,298
Likes: 4
From: American Canyon Lethal Injection
Also as memtioned not letting the cats warm up really good may be part of the problem also.
Thanks for the input..
Sleeper
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,298
Likes: 4
From: American Canyon Lethal Injection
[QUOTE=cruisemon;1561472624]
Well you maybe correct in the cats not being hot enough.
Although I had the car on the freeway for a long run..when I got to the smog shop the car sat for maybe 20-25 minutes before the smog was done.
So between maybe i.e. bad tune, bad O2s and not hot enough cats it didn't pass.
1. I plan to replace the O2s because I had gotten a code on the pass side after the LTs were installed for the O2.
2. have the tuner look at it for being rich and see if he can tune it leaner.
Thanks for your input..
Sleeper
I have mods of course. H/C and long tube headers with high flow cats.QUOTE]
Well let's see. A lumpy cam and flunk the sniff test. Hmmmmmm. I think a better tune is in order.
I think THE question on EVERY California Vette owner is how you got the long tubes past the check/expect to get the LT's past the check. The high flow cats are harder to light off and they are far enough from the cylinder to mean the exhaust temp is down as well. I don't know if it will help, or if this will keep enough residual heat to keeps the cats cooked off, but jump on the freeway and drive at maximum allowable speed for 30 minutes or so and then check the sniffer again. And IF this works, please DO tell us how you got the LT's past the inspection.
Charlie
Well let's see. A lumpy cam and flunk the sniff test. Hmmmmmm. I think a better tune is in order.
I think THE question on EVERY California Vette owner is how you got the long tubes past the check/expect to get the LT's past the check. The high flow cats are harder to light off and they are far enough from the cylinder to mean the exhaust temp is down as well. I don't know if it will help, or if this will keep enough residual heat to keeps the cats cooked off, but jump on the freeway and drive at maximum allowable speed for 30 minutes or so and then check the sniffer again. And IF this works, please DO tell us how you got the LT's past the inspection.
Charlie
Although I had the car on the freeway for a long run..when I got to the smog shop the car sat for maybe 20-25 minutes before the smog was done.
So between maybe i.e. bad tune, bad O2s and not hot enough cats it didn't pass.
1. I plan to replace the O2s because I had gotten a code on the pass side after the LTs were installed for the O2.
2. have the tuner look at it for being rich and see if he can tune it leaner.
Thanks for your input..
Sleeper
Race Director
Joined: Dec 2000
Posts: 19,304
Likes: 85
From: San Diego CA
Here's what my recent and original (when new) smog test results looked like:
http://forums.corvetteforum.com/show....php?t=1703300
It just doesn't make sense to me why the "MAX" HC number has plummeted. This needs to be looked into.
http://forums.corvetteforum.com/show....php?t=1703300
It just doesn't make sense to me why the "MAX" HC number has plummeted. This needs to be looked into.
Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,298
Likes: 4
From: American Canyon Lethal Injection
Here's what my recent and original (when new) smog test results looked like:
http://forums.corvetteforum.com/show....php?t=1703300
It just doesn't make sense to me why the "MAX" HC number has plummeted. This needs to be looked into.
http://forums.corvetteforum.com/show....php?t=1703300
It just doesn't make sense to me why the "MAX" HC number has plummeted. This needs to be looked into.
1. Bad O2 (s) front.
2. Tuned too rich.
3. Cats not hot enough...
The above I'm sure would cause this reading.
Sleeper
Racer
Joined: Feb 2007
Posts: 431
Likes: 5
From: Chico CA
Don't forget to check for exhaust leaks. My car threw a code for right rear O2 sensor, but it turned out to be just loose nuts on the right flange ahead of the cat. Tightened things up and the mileage shot up, and the code went away. Would probably have failed smog, if it had been on the machine - enough rich to affect gas mileage, but still reading lean on the RR O2 sensor... 
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Thread Starter
Le Mans Master
Joined: Aug 2003
Posts: 9,298
Likes: 4
From: American Canyon Lethal Injection
Don't forget to check for exhaust leaks. My car threw a code for right rear O2 sensor, but it turned out to be just loose nuts on the right flange ahead of the cat. Tightened things up and the mileage shot up, and the code went away. Would probably have failed smog, if it had been on the machine - enough rich to affect gas mileage, but still reading lean on the RR O2 sensor...
Thanks for the input..I'll do that before installing any O2s. I only have front O2 to deal with..
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Here's what my recent and original (when new) smog test results looked like:
http://forums.corvetteforum.com/show....php?t=1703300
It just doesn't make sense to me why the "MAX" HC number has plummeted. This needs to be looked into.
http://forums.corvetteforum.com/show....php?t=1703300
It just doesn't make sense to me why the "MAX" HC number has plummeted. This needs to be looked into.
Race Director
Joined: Dec 2000
Posts: 19,304
Likes: 85
From: San Diego CA
...my thought, EXACTLY! It's almost as if they are trying to guarantee that by 10 years of age, you'll have to trash your car and buy a new one. That would mean that by 2011 the new MAX HC will be about 20 for C5s!
